1. Field of the Invention
The present invention relates to drive control technology employed in drivers comprising an electric drive unit. As such drivers, for example, there are electric traveling vehicles such as an electric car, electric wheelchair, electric cart, and so on which in particular comprise an actuator as the electric motor. The drive control technology of the present invention may also be employed in drivers structuring electric construction machinery, electric welfare equipment, electric robots, electric toys, electric airplanes, and electric optical devices such as cameras and projectors, among others. Moreover, the present invention may also be applied to domestic electric appliances such as air conditioners, fan motors, stoves, and the like.
2. Background Art
An electric traveling vehicle moves by the drive control means rotationally controlling the electric motor. The drive control means adjusts the speed of the electric vehicle by adjusting the speed (rotational speed) of this electric motor. Speed is adjusted by making the supply voltage supplied to the electric motor variable and suppressing the power supply to the electric motor. For example, when the passenger operates the accelerator pedal or lever and the acceleration based on such manipulated variable is set in the drive control means, the electric vehicle will travel under the set acceleration. When the vehicle reaches a prescribed speed and the passenger returns the accelerator pedal or accelerator lever to a prescribed level, the speed of the electric vehicle is maintained at a prescribed value.
Meanwhile, when decelerating the vehicle, the passenger sets the accelerator pedal or accelerator lever to a position for decelerating the vehicle. The drive control means thereby performs braking control for decelerating the electric motor to a prescribed speed. When the operational status of the accelerator pedal or accelerator lever is maintained, the vehicle speed is maintained at a prescribed value.
Nevertheless, since the adjustment of the vehicle speed is not conducted by the driver, the vehicle speed would not be constant under certain travel path conditions; for example, slopes and surface frictions of the travel path, and the passenger had no choice but to frequently perform acceleration operations in order to adjust the vehicle speed.
In consideration of the above, technology referred to as cruise control is provided. This technology maintains the vehicle speed at the designated speed even though disturbances occur to the vehicle speed.
In cases of electric motors such as a stepping motor having a high control precision of rotational speed, favorable speed control can be realized. With standard AC motors or DC motors, however, only rough rotation control such as rotating when the power is turned on and stopping when the power is turned off is conducted, and technology capable of minutely and precisely controlling the rotational speed of motors has not yet been established to date.
Further, when employing a transmission means such as a continuously variable transmission, although the revolution of the end wheels could be changed precisely even when setting the rotational speed of the motor to be constant, the number of components would increase and the weight would become heavy. Thus, this is unfavorable in lightweight compact electric cars, electric wheelchairs and passenger carts requiring tight turning circles.
Moreover, the drive control means is structured of a microcomputer, and, when the electric motor is in a state of high velocity revolution, the detection signal frequency from the electric motor is high, and the drive control processing within the computer will not be in time. Thus, there is a problem in that minute and rapid control cannot be sufficiently implemented to a high-speed electric motor.
Further, since the power control loss is discharged as heat, the conversion efficiency was inferior upon converting the power energy to the drive energy of the electric driver.
In light of the above, an object of the present invention is to provide drive control technology capable of implementing control that sufficiently corresponds to high-speed motions of an electric drive unit. Another object of the present invention is to provide drive control technology enabling accurate operation of the actuator under a designated operational status. A still another object of the present invention is to provide drive control technology capable of effectively using the braking power that is generated during the braking control of the actuator. A further object of the present invention is to use PLL control as the foregoing drive control technology. A still further object of the present invention is to provide drive control technology capable of controlling the power of the electric drive unit based on the operational status of the electric drive unit in addition to the foregoing PLL control. A yet further object of the present invention is to control the motion of the electric drive unit by changing the duty of the supply voltage to the electric drive unit, or changing the voltage. A yet further object of the present is to change the braking characteristics of the actuator by controlling the braking power. A yet further object of the present invention is to provide a drive control device and drive control method comprising this drive control technology. A yet further object of the present invention is to provide a driver, particularly an electric vehicle, controlled with this drive control technology.